To date, much effort has been extended toward managing and improving the health, safety, and performance of bridge structures. Information gathering methods, such as on-site inspections, data acquisition systems, audio and visual monitors, and the like assist in the evaluation of a bridge's structural health and safety. Moreover, corrosion protection, lighting, cleaning, and repair programs are examples of remedial efforts used to promote a bridge structure's health, safety, and performance. A number of these applications, both on the information gathering side and on the remedial side, utilize low amperage power sources. In the past, implementation of structural health and safety applications have be hampered by the lack of availability of a reliable, cost effective, and low maintenance power source.
A significant amount of kinetic energy is absorbed or transmitted through the roadway or bridge structure due to vehicles traversing the structure or by seismic or wind activity moving the structure. It is possible to capture some of this kinetic energy by utilizing piezoelectric materials which are strained during vehicle passage seismic activity, wind, or other events which impart energy of motion to the expansion joint. As an example of the availability of such energy for harvest by piezoelectric materials, piezoelectric fibers may be embedded within the tires of a vehicle to capture or “harvest” kinetic energy which can then be transformed and utilized within the vehicle. Using presently known means, this vehicle captured kinetic energy cannot be directly utilized for applications on a bridge, roadway or other structure. Further, designs that utilize piezoelectronics rely upon small amplitude material straining are best suited for vibration waveforms that are of long duration and high frequency. As such, piezoelectric based energy harvesting systems are impractical for the type of vibrations experienced by expansion joint systems.
Displacement driven energy generation refers to generators that utilize the relative displacements between components for energy generation, and do not rely upon material straining to produce energy. Displacement driven energy harvesting can be much more efficient than piezoelectric-based energy harvesting systems for the type of vibrations experienced by expansion joint systems.
Both piezoelectric and displacement driven energy harvesters have been proposed in attempts to capture the kinetic energy in water, which is manifested as waves and turbulence. Heretofore, however, it has not been known to incorporate energy harvesting, transforming and applying means within a bridge, roadway, or architectural structure expansion joint system.
Accordingly, it remains desirable in the art to provide means for harvesting kinetic energy within a bridge, roadway, or architectural structure expansion joint system, transforming the kinetic energy to electrical energy, and utilizing the electrical energy for structural health, safety and performance applications directly on the roadway, bridge, or architectural structure, and an expansion joint system incorporating a energy harvesting, transforming, and utilizing means. It is also desirable that the means for harvesting, transforming, and applying the energy be compact, environmentally durable, substantially maintenance free, and be able to withstand hundreds of millions of large amplitude displacement cycles. It is also desirable that the means should be able to effectively utilize expansion joint displacements, which are on the scale of a millimeter, high force, intermittent, and of moderate frequency.